Xbee s1 in API mode

We are currently working on a project of “Soil Moisture Measurement of an agricultural land”.In this project, we are using the Xbee S1 modules for wireless communication. In our setup, we havea Xbee connected to the PC in which LabView is installed to check the output. This Xbee is
configured as a co-ordinator(Receiver). We use another two Xbee modules which are connected to the soil moisture sensor and to the arduino. The transmitter code is uploaded to the arduino board.These Xbee modules act as the transmitters.The soil moisture value is transmitted to the
receiver wirelessly through Xbee. Now the problem is, we wanted to configure the Xbee in API mode so that the data can be easily transmitted simultaneously from both the nodes(transmitters)in the form of packets.At the receiver side, we need to know from which node(transmitter), the packet is arriving. But we are unable to get that.Can someone help me with this.

IF your coordinator is in API mode (ATAP1 or 2), then a standard receive packet from over the air will be in the form of a type 0x80 or 0x81.